Various security mechanisms may be implemented to protect reprogrammable systems deployed in the field such as set top boxes in a video distribution system. Occasionally, entry points to restricted-access functionality on such systems may be neglected by resident security code and/or circuitry. Unauthorized users may discover ways to navigate around existing security obstacles and gain prohibited access. In a reprogrammable security system, security software may be updated with subsequent versions of code that correct errors found in prior versions. Security code updates may be distributed by a control center and downloaded in the field. Further access by unauthorized users may require new approaches to the problem.
It may be difficult for an unauthorized user to gain restricted access to a device in the field by making modifications to resident security code. Such an attempt would require extensive knowledge and skill on the part of the user due to cryptographic applications. An alternate means may be to make a copy of a prior version of security code whose design is vulnerable to breach, and download it onto the device over a subsequent version of improved code. The system may perceive the copy to be a properly authorized unit of code and may accept it readily into the system. With the prior version of code in place, the unauthorized user may again gain access using the original method to circumvent existing security obstacles. New techniques for securing reprogrammable systems may be needed to prevent future incursions.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with the present invention as set forth in the remainder of the present application with reference to the drawings.